The presently disclosed subject matter relates to an electrical impedance measuring apparatus which is called the EIT (Electrical Impedance Tomography) or the like.
In the EIT, the impedance distribution of the chest is continuously displayed as a tomographic image, or, in place of or together with the tomographic image, an impedance variation waveform is displayed. In artificial ventilation therapy of respiratory disease such as ARDS (Acute Respiratory Distress Syndrome), a diagnosis is performed based on EIT images.
There is a related-art technique in which, in the EIT, the lung region in a tomographic image is segmented into several ROIs (Regions of Interest), and the ratio of the value of an impedance integration of an ROI to that of the all ROIs is displayed in the form of a waveform or a numerical value (see U.S. Pat. No. 8,321,007).
The EIT images show the aerated state of the lungs. In treatment of ARDS or the like, the state where aeration spreads over not only the ventral side but also the dorsal side is used as an index indicating a good state. Depending on the ratio of the value of an impedance integration of an ROI to that of the all ROIs which is obtained as disclosed in U.S. Pat. No. 8,321,007, however, it is difficult to intuitively know the spread of aeration from the ventral side to the dorsal side. Moreover, also depending on a tomographic image and impedance variation waveform in the EIT, it is difficult to know the spread of aeration from the ventral side to the dorsal side. Therefore, there is a need to develop an electrical impedance measuring apparatus which enables the spread of aeration from the ventral side to the dorsal side to be adequately known in a hyperextension state.